Chemical Oxygen Demand Rejection Research Articles

Development of metakaolin-based geopolymeric asymmetric membrane for oil-in-water emulsion microfiltration

This study investigated the potential application of geopolymeric material for the separation of oil-in-water emulsions in wastewater treatment. For the first time, an asymmetric membrane made of geopolymers was developed for this specific separation process. The performances of the geopolymeric membrane in oil separation were compared with those obtained by a commercial ceramic membrane. The study also aimed at exploring the effects of emulsion formulation and emulsion properties (surfactant type and concentration, pH, and zeta potential) and membrane parameters (surface charge and material) on permeate volumetric flux and chemical oxygen demand (COD) rejection. Emulsions were prepared using 3% (w/v) dodecane oil in distilled water, with surfactant concentrations of 1x and 10x critical micelle concentration (CMC) and three surfactants of different nature (Oleth-10, Brij 76, and CTAB) at pH values of 2, 5, and 8. Results showed that for the best operating conditions of the geopolymeric membrane, initial and final permeate flux values of 42 and 26 L h−1 m−2, respectively, were achieved. COD rejection values ranged from 95.0 to 99.4% using the geopolymeric membrane thus indicating a very similar behavior between geopolymeric and ceramic membranes. These findings suggest that geopolymers are promising to produce membranes for oil-in-water emulsion microfiltration, promoting an interesting alternative for the treatment of industrial wastewater more sustainable in terms of environmental effects and costs compared to ceramic membranes.

Application of BiVO4/TiO2/CNT Composite Photocatalysts for Membrane Fouling Control and Photocatalytic Membrane Regeneration during Dairy Wastewater Treatment

This study aimed to investigate the performance of composite photocatalytic membranes fabricated by incorporating multiple nanoparticles (TiO2, carbon nanotubes, BiVO4) into polyvinylidene fluoride membrane material for real dairy wastewater treatment. The composite photocatalytic membranes exhibited superior antifouling behavior, lower filtration resistance, better flux, and higher flux recovery ratio than the pristine membrane. Salinity, pH, and lactose concentration are determinant factors that affect filtration resistance and rejection performance during the ultrafiltration of dairy wastewater. Generally, higher irreversible and total resistances and slightly lower chemical oxygen demand (COD) rejections were found at higher salinity (expressed by electric conductivity values of >4 mS/cm) than lower salinity (<4 mS/cm) levels. The presence of lactose in dairy wastewater increased irreversible resistance and severely reduced COD rejection during ultrafiltration due to the ability of lactose to pass through the membranes. It was ascertained that membranes require further treatment after filtrating such wastewater. Lower resistances and slightly better COD rejections were observed at pH 7.5 and pH 9.5 compared to those observed at pH 4. Photocatalytic membranes fouled during the ultrafiltration of real dairy wastewater were regenerated by visible light irradiation. The membrane containing all constituents (i.e., TiO2, carbon nanotubes, and BiVO4) showed the best regeneration performance, exceeding that of the pristine membrane by 30%.

Evaluating Laboratory Side-stream Membrane Bioreactor and Nanofiltration System for Treating Domestic Wastewater and Reuse

This paper presents Membrane Bioreactor (MBR) and Nanofiltration (NF) systems as alternative and effective approaches for treatment and reusing domestic sewage. The goal is to investigate the general performance of a membrane bioreactor and nanofilteration membrane ability to satisfy water reuse requirements using water quality index such as total suspended solids (TSS), chemical oxygen demand (COD), and ammonia (NH3). The findings show that the MBR system produces high-quality permeating water. TSS, COD and NH3 rejection rates were 99%, 90.3%, and 82.5% (on average). In addition, MBR technology is quite successful as a pre-NF treatment. We also evaluated how pressure and temperature affect the effectiveness of the NF membrane removal of TDS, COD, ammonia, and permeating flux. The results showed that the applied pressure has a favorable impact on the total removal rate; however, the feeding temperature has a negative impact. The feeding temperature, in addition to pressure, has a good influence on the flux of the NF system.

TiO2 ceramic membrane decorated with Fe3O4–Ag composite nanoparticles for produced water treatment

This study focused on the surface modification of commercial TiO2 membranes with Fe3O4 decorated silver (Ag) nanoparticles (Fe3O4–Ag) via chemical attachment. Firstly, the Ag concentration on Fe3O4 was optimized, and different composites were prepared and characterized. Secondly, the optimal composite was used to prepare novel TiO2/Fe3O4–Ag ceramic membranes via surface coating through tetraethyl orthosilicate (TEOS) crosslinking. The membranes were characterized using SEM, EDX, FTIR, XRD, and contact angle. Biofouling resistance of the membranes was investigated using the Coomassie Blue dye method. The coated membranes were tested for water flux, chemical oxygen demand (COD) rejection, and biofouling resistance. Results showed that all coated membranes exhibited higher water flux. For example, the membrane with a 1.25 wt% Fe3O4–Ag coating showed the highest filtration flux of 1445 L/m2h (LMH) compared to the pristine membrane (379 LMH) without compromising the COD rejection. The resistance of the membrane to biofouling increased with the increase of Fe3O4–Ag nanoparticle concentration. The obtained results demonstrate the great potential of TiO2/Fe3O4–Ag ceramic membranes for the treatment of produced water.

Use of ultrafiltration ceramic membranes as a first step treatment for olive oil washing wastewater

Olive oil is a food product in great demand throughout the world, its production generating large volumes of wastewater with a high organic load, where phenolic compounds are present. These compounds have outstanding antioxidant characteristics, so their recovery is of great interest. In this way, the treatment of these wastewaters should be based on reusing water and, at the same time, on recovering valuable compounds. Ultrafiltration with ceramic membranes (5, 15 and 50 kDa) is proposed as a first treatment step for olive oil washing wastewater (OOWW) from the continuous two-phase centrifugation process. The effect of cross flow velocity and transmembrane pressure was evaluated against permeate flux values and the removal of turbidity, colour, chemical oxygen demand (COD), sugars and the phenolic compounds recovery. The CFV had a great influence on the removal of colour and turbidity. COD rejection increased with increasing TMP, being the highest rejection obtained under the most extreme conditions. The rejection of phenolic compounds and sugars did not show great variation between conditions. The 50 kDa membrane was the one that presented the largest permeate flux decline and the lowest permeability recovery after the cleaning, confirming the great fouling that this membrane suffered. The 15 kDa membrane at the operating conditions of 3 m.s-1 and 3 bar was observed as a good option to eliminate much of the colour (72%) and turbidity (99%) and to reduce considerably the organic load (54%) without greatly affecting the concentration of phenolic compounds (rejection of 21%) for future recovery.

Reusability of Nano-Fe3O4/Polyvinylidene Difluoride Membrane for Palm Oil Mill Effluent Treatment

Membrane reusability determines the economic sustainability of separation process. However, the reusability of membrane was deduced by the antifouling properties, while the actual reuse performance of membrane using palm oil mill effluent (POME) is rarely reported. This study investigates the reusability of nano-Fe3O4/PVDF (PVDF1) membrane for POME treatment. The chemical oxygen demand (COD), total suspended solid (TSS) of permeate, molecular weight cut off (MWCO), pure water flux (PWF) and contact angle (CA) of membranes were also determined. Result showed that the neat membrane (PVDF0) and PVDF1 exhibited ~77°, ~342 L/(m2.h) and ~70°, 278 L/(m2.h) for CA and PWF, respectively, due to the small MWCO in PVDF1. The POME flux was maintained at ~16 L/(m2.h) in 5 cycles of filtration process. The COD rejection was higher for PVDF 1 compared to PVDF0, and PVDF1 showed consistent ~58 % COD and ~98 % TSS removal in all the cycles. The good performance of PVDF1 due to the presence of nano-Fe3O4, improved the membrane hydrophilicity and tailored the membrane pore size for POME treatment.
 HIGHLIGHTS
 
 Membrane reusability determines the economic sustainability of separation process
 Nano-Fe3O4 improves the hydrophilicity of PVDF membrane
 Nano-Fe3O4 tailors the pore size of PVDF membrane for POME treatment
 POME flux was maintained at ~16 L/(m2.h) for 5 cycles of filtration process
 The membrane can be reused for minimum 5 cycles with consistent COD and TSS removal
 
 GRAPHICAL ABSTRACT

Membrane-based conceptual design of reuse water production from candy factory wastewater.

Intense pressure on water resources has led to efforts to reuse reclaimed processing wastewater in the food industry. There are tight rules for water quality, but efficient separation technologies such as reverse osmosis possess good possibilities for water reuse. This study developed a membrane-based reuse water concept for wastewater from the candy industry emphasizing the pre-treatment stage in the concept to reduce fouling. The wastewater contained suspended solids, sugar compounds and the ingredients for candy gelation, which had a tendency to foul membranes, making pre-treatment essential for a successful concept. Cross-rotational ultrafiltration, which featured enhanced fouling prevention for membranes, functioned well for the removal of challenging substances. Conventional filtration technologies were impractical due to a low flux, even when the viscosity of the wastewater was reduced using surfactants. The wastewater had a high chemical oxygen demand, meaning that there was a strong fouling potential for reverse osmosis membranes, but also high osmotic pressure. A spiral wound reverse osmosis functioned well when the wastewater was pre-treated, and it produced good quality water with respect to all the other studied parameters except the chemical oxygen demand. However, chemical oxygen demand rejection was 99% since the concentration in the wastewater was originally very high.

Comparison of different ultrafiltration membranes as first step for the recovery of phenolic compounds from olive-oil washing wastewater

The production of olive oil generates wastewater with a high organic load and toxicity due to the high concentration of phenolic compounds. In recent years, the study on the treatments of these waters has been intensified together with the search for a process to recover these phenolic compounds due to their great antioxidant potential. All this with the aim of implementing the concept of circular economy. In this study, four different organic ultrafiltration membranes were evaluated in order to recover the phenolic compounds present in olive oil washing wastewater (OOWW) from an oil mill in the Valencian Community (Spain). The tested membranes differ in materials and molecular weight cut-off (MWCO): two permanently hydrophilic polyethersulfone (PESH) membranes with MWCO of 4 and 50 kDa, respectively, one polyethersulfone (PES) membrane with a MWCO of 5 kDa and a regenerated cellulose acetate (RCA) membrane with a MWCO of 10 kDa. Transmembrane pressure (TMP) and crossflow velocity (CFV) were varied from 1 to 3 bar and from 1.5 to 3.4 m·s−1, respectively. The effectiveness of the different membranes and operating conditions were evaluated comparing the permeate flux and the rejection of chemical oxygen demand (COD) and total phenolic compounds (TPhs). The membranes with lower MWCO showed stable permeate fluxes without significant changes over time, while the 50 kDa membrane showed a gradual decrease, without achieving a stable flux. Low rejection of phenolic compounds was observed in all cases, while the rejection of COD varied between 19.5 % and 62.9 % depending on the membrane and operating conditions tested. Except for the 50 kDa PESH membrane, initial permeability recovery greater than 95 % was achieved with a 35 °C water rinse, indicating that membrane fouling was not severe. Since the aim was to recover the TPhs in the permeate stream and separate them from the organic matter, the 5 kDa PES membrane at 2 bar and 2.5 m·s−1 was considered to be the best option. At those conditions a stable permeate flux of 40 L·h−1·m−2 was obtained, while the lowest TPhs rejection was observed (8.01 %) with a high COD rejection (61.18 %).

Effective treatment of the wastewater from ceramic industry using ceramic membranes.

Emissions of organic compounds, heavy metals and chemicals used in the ceramic industry cause significant organic and inorganic pollution of water. The effluent must be treated before it is discharged into a water body. International and EU laws control the chemical oxygen demand (COD) of the wastewater. Conventional technologies, such as sedimentation, flocculation and biological treatment, have lots of drawbacks, whereas membrane technologies give many benefits, as they are chemical-free and allow a reduction of the treatment steps. One-step wastewater nanofiltration with ceramic membranes of 450 Da cut-off is able to reduce the COD of ceramic wastewater to a sufficient level. However, the working time without cleaning is limited and the rejection of membranes can be significantly reduced due to fouling. Multistage filtration can be the solution. Filtration experiments with various combinations (MF, UF and NF) of ceramic membranes were performed at a laboratory scale with single-channel membranes and at pilot scale with 7-, 19- and 151-channel membranes in order to permanently reach the limit value of a COD below 80 mg/L and to increase the operating time. Four types of membranes were sequentially tested in the cross-flow mode: MF (200 nm pore size), UF (2,000 Da), NF (450 Da) and NF (200 Da). 5-day Biological Oxygen Demand (BOD) tests were performed in order to examine the wastewater biodegradability. The test results with single-channel membranes showed that in terms of the highest COD rejection and the highest permeability, the best combination was that of MF and UF membranes. Here, UF membranes were sufficient to reach the limit values. As for the multi-channel membranes, the combination of MF and NF (450 Da) was the best and the final COD concentration ranged from 11 to 48 mg/L. 5-day BOD bottle tests showed a COD/BOD ratio of 3.8, which opened up possibilities for combined treatment.

Comparative study of embedded functionalised MWCNTs and GO in Ultrafiltration (UF) PVC membrane: interaction mechanisms and performance

ABSTRACT This work presents the development of polyvinyl chloride/functionalised multi-carbon nanotube (PVC/F-MWCNT) membranes and PVC/graphene oxide (PVC/GO) membranes for the improved removal of chemical oxygen demand (COD) from actual petroleum wastewater. Also, this work for the first time presents the proposed interaction mechanism between the contents of PVC/GO and PVC/F-MWCNT membranes as well as the interaction mechanism of each composite membrane with water molecules. The effect of both F-MWCNT and GO content on the characteristics and performance of the PVC/F-MWCNT membrane and PVC/GO membrane were studied. Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscope (SEM), atomic force microscopy (AFM), contact angle (CA), differential scanning calorimetry (DSC), porosity and tensile strength were used to examine the properties of F-MWCNT, GO, PVC/F-MWCNT and PVC/GO membranes. The composite membranes’ performance was studied by measuring the rejection of chemical oxygen demand (COD) and mass flux. It was found that F-MWCNTs and GO played significant roles in the membranes’ structural morphology. A significant improvement was obtained in the CA, porosity and tensile strength of the membranes by embedding the PVC casting solution with 0.12 wt% of each F-MWCNTand GO. The PVC/F-MWCNTs membrane showed higher performance in term of mass flux and COD rejection that reached 88.9%, which makes using a PVC/F-MWCNTs membrane preferable to remove COD from petroleum wastewater.

Operating Conditions Optimization via the Taguchi Method to Remove Colloidal Substances from Recycled Paper and Cardboard Production Wastewater.

Optimization of the ultrafiltration (UF) process to remove colloidal substances from a paper mill’s treated effluent was investigated in this study. The effects of four operating parameters in a UF system (transmembrane pressure (TMP), cross-flow velocity (CFV), temperature and molecular weight cut-off (MWCO)) on the average permeate flux (Jv), organic matter chemical oxygen demand (COD) rejection rate and the cumulative flux decline (SFD), was investigated by robust experimental design using the Taguchi method. Analysis of variance (ANOVA) for an L9 orthogonal array were used to determine the significance of the individual factors, that is to say, to determine which factor has more and which less influence over the UF response variables. Analysis of the percentage contribution (P%) indicated that the TMP and MWCO have the greatest contribution to the average permeate flux and SFD. In the case of the COD rejection rate, the results showed that MWCO has the highest contribution followed by CFV. The Taguchi method and the utility concept were employed to optimize the multiple response variables. The optimal conditions were found to be 2.0 bar of transmembrane pressure, 1.041 m/s of the cross-flow velocity, 15 °C of the temperature, and 100 kDa MWCO. The validation experiments under the optimal conditions achieved Jv, COD rejection rate and SFD results of 81.15 L·m−2·h−1, 43.90% and 6.01, respectively. Additionally, SST and turbidity decreased by about 99% and 99.5%, respectively, and reduction in particle size from around 458–1281 nm to 12.71–24.36 nm was achieved. The field-emission scanning electron microscopy images under optimal conditions showed that membrane fouling takes place at the highest rate in the first 30 min of UF. The results demonstrate the validity of the approach of using the Taguchi method and utility concept to obtain the optimal membrane conditions for the wastewater treatment using a reduced number of experiments.

Effect of landfill leachate ageing on ultrafiltration performance and membrane fouling behaviour

In this study, the effect of ageing on the performance and fouling mechanisms in the ultrafiltration of landfill leachates using titania-zirconia (ZrO2-TiO2) tubular membrane was thoroughly studied. Results revealed that the maturation of the leachate has a positive effect on its ultrafiltration, with a twofold higher final permeability compared with the young one. This is the result of the higher organic load, particularly that corresponding to proteins and carbohydrates, of the young leachate.Resistance-in-series analysis demonstrated that the loss of permeability was mainly due to reversible fouling, caused by cake filtration. Either irrecoverable or irreversible fouling were scarce and not conditioned by the stage of maturation of the leachate. Chemical oxygen demand (COD) rejection for the mature leachate varied with volume concentration ratio (VCR) following an approximately sigmoidal shape, from an initial value of 18.5% to a final one of 49.6%, with the faster increase at VCR ranging from 1.2 to 1.7, due to the permeation of fatty acids by the ultrafiltration (UF) membrane. On the other hand, COD rejection remained approximately constant at 48% during the ultrafiltration of the young leachate, which can be attributed to the presence of higher molecular weight compounds in its composition.

Preparation and characterization of nano-filtration and its photocatalytic abilities via pre-coated and self-forming dynamic membranes developed by ZnO, PAC and chitosan.

In the current work, novel dynamic membranes (DM) were tested and introduced for cheese whey wastewater treatment based on resistant and inexpensive materials, polyesters, and chitosan. For the investigation of dynamic membrane (pre-coated and self-forming) characterizations, polyester as a low-cost and natural material with chitosan were chosen to provide the support of the target membrane. The inherent antifouling character of chitosan accompanied by its high hydrophilicity have made this polymer known as an attractive agent for membrane-based wastewater treatment operations. Zinc oxide (ZnO) and powdered activated carbon (PAC) were employed as the dynamic layer. Neat polyester had a chemical oxygen demand (COD) rejection ratio of about 57.61%, but the flux declined sharply. The higher removal efficiency was for the self-forming type: total phosphate (94%) and citrate (95.5%). Fouled dynamic membranes were backwashed by sodium dodecyl-sulphate (SDS), warm water, and distilled water. Results demonstrated that the pre-coated was reduced and fouling increased the flux recovery rate (FRR) (9.1%) while use of the self-forming DM exhibited an aggravation of fouling by decreasing of support FRR (11.1%). It was found that by substitution of deionized water and hot water with SDS, FRR was enhanced. In the following, the photocatalytic ability of the product was investigated. The UV light source increased the removal ratio and FRR. For example, self-forming COD rejection was enhanced (6.63%).

Effect of embedding MWCNT-g-GO with PVC on the performance of PVC membranes for oily wastewater treatment

In this work, polyvinyl chloride/multi-walled carbon nanotube-grafted-graphene oxide (PVC/MWCNT-g-GO) membranes were fabricated by employing a classical phase inversion method for use in the Al-Dura Refinery (Baghdad, Iraq) wastewater treatment. The effects of MWCNT-g-GO contents on the properties and performance of PVC/MWCNT-g-GO membranes (i.e., 0.0599, 0.119, and 0.219 wt.%) were investigated. Scanning electron microscope (SEM), Fourier-transform infrared spectroscopy (FTIR), atomic force microscopy (AFM), X-ray diffraction (XRD), differential scanning calorimetry (DSC), contact angle (CA), porosity, and mechanical properties were used to characterize the MWCNT-g-GO and composite membranes. The membrane performance was characterized by liquid permeation flux and chemical oxygen demand (COD) rejection. The SEM and AFM results showed significant effects of MWCNT-g-GO on the structural morphology of the membranes. Also, it was found that the addition of a 0.119 wt.% MWCNT-g-GO membrane greatly improved the CA and porosity, from 74.5° to 13.9° and from 69.3% to 81.4%, respectively. Adding 0.219 wt.% of MWCNT-g-GO to the casting solution produced a major positive impact in the membrane mechanical properties. With 0.119 wt.% of MWCNT-g-GO (e.g., 254 L/m2·h), the membrane fostered increases in the water permeation flux that were 66% greater than when using the neat PVC (e.g., 153 L/m2·h). The COD rejection of the prepared membranes also improved significantly, from 60% for neat PVC to 88.9% after adding 0.119 wt.% of MWCNT-g-GO.

The valorization of biogas slurry with a pilot dual stage reverse osmosis membrane process

Biogas slurry is an environmental pollution source if it is discharged without proper treatment. In this work, a membrane system is designed to concentrate, and hence to recover the nutrient in the biogas slurry. The effects of pre-treatment technology, pH, temperature, operating pressure and module types of the reverse osmosis unit were studied via analyzing the chemical oxygen demand (COD), ammonia nitrogen, total nitrogen, conductivity in the permeate and retentate, and the volume concentration ratio. A dual stage reverse osmosis (RO) process is also applied to further enhance the performance, the concentration ratio reaches above 5 within 80 mins of operation, while the nutrient recovery and water recovery rates are 98% and 92.52%, respectively. The COD and ammonia nitrogen rejection rates are 99.41% and 99.11%, respectively; the quality of the permeate is in accordance with the national standard for water discharging.

COD reduction of process wastewater with vacuum evaporation

Abstract Washing detergents in process wastewaters from fine chemical industry produce high Chemical Oxygen Demand (COD), which poses a serious environmental problem. Method has to be found, which follows the principles of circular economy so that the treated water can be recycled or reused. Heat pump vacuum evaporator is evaluated in order to reduce the Chemical Oxygen Demand of process wastewater with washing detergent content from initial 7500 mg O2/L to a lower value below the effluent limit , which is 1000 mg O2/L. Yield and COD rejection are determined for the evaluation of selected treatment. Experiments are investigated with LED Italia R150-v3 pilot apparatus. Different evaporation pressures were applied during measurements. It The highest removal or reduction of in the Chemical Oxygen Demand was reached certainly using the lowest possible pressure, which is 40 mbar.

Combination of Coagulation-flocculation and Ultrafiltration Processes using Cellulose Acetate Membrane for Wastewater Treatment of Tofu Industry

The tofu industry is generally a household-scale industry so that the efficiency of water used and wastewater treatment are mistreated. Wastewater from tofu industry is very hazardous when discharged directly into the aquatic environment as it contains high organic pollutants which is indicated by high concentrations of BOD (biological oxygen demand), COD (chemical oxygen demand), TSS (total suspended solid), TDS (total dissolved solid) and turbidity. The optimization of wastewater treatment process is needed to meet the quality standards set by the government and also needed to obtain more effective and efficient effluent treatment. The aim of this study is to evaluate the performance of combination coagulation-flocculation and ultrafiltration processes for tofu industry wastewater treatment. The process of pretreatment coagulation and flocculation using poly aluminum chloride (PAC) was conducted to extend the life of the ultrafiltration membrane and improve the performance of ultrafiltration membrane separation. The experimental results showed that TSS and turbidity decreased with precipitation time whereas COD did not significantly change. TDS after coagulation-flocculation has increased due to the addition of PAC. The TSS, TDS, COD and turbidity of wastewater were drastically reduced after experiencing ultrafiltration process. After the ultrafiltration process, the TSS, Turbidity, COD and TDS rejection were 98.8%, 98.1%, 71.0% and 50.6%, respectively.

Hydrophilic modification of a poly(ether sulfone) flat-sheet ultrafiltration membrane applied to coking sewage

In this article, a new modified poly(ether sulfone) flat-sheet ultrafiltration membrane, which is expected to effectively handle coking sewage, was prepared by an immersion precipitation phase-inversion technique to settle the wastewater treatment problem in coking plants. Nanometer TiO2 particle–poly(ethylene glycol) (PEG) blends were used as additives to modify the membranes by a blending method. The effects of different PEG mass concentrations on the membrane structure and properties were studied. The pure water flux and chemical oxygen demand (COD) rejection rate were analyzed as aggregative indicators by the comprehensive evaluation method, and then, the optimal PEG mass concentration was determined. The results show that the best modified effect was obtained at a PEG mass concentration of 0.25%. When coking sewage in a secondary settling tank was filtered with such membranes, the COD rejection rate reached 90.68%, and the water flux was 127.21 L m−2 h−1. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45149.

A new approach to evaluate membrane performance: COD and EC rejection rates

Olive mill wastewater (OMW), which contains abundant soluble and particulate matter, negatively influences the receiving environment. Membrane processes have the potential to treat OMW. Electrical conductivity (EC), which is very high in OMW, is one of the key factors of membrane processes. The EC value of the OMW sample used in this study was higher than the common values, and this situation resulted in high osmotic pressure. Several samples with different influent EC values were fed to a reverse osmosis (RO) system. The osmotic pressure values for each influent EC were calculated. The relationship between the osmotic pressure and influent EC values was nonlinear. The permeate flux could not be achieved for some applied pressures and influent EC values because of the high osmotic pressure of the feedwater. Moreover, the terms of the chemical oxygen demand (COD) rejection rate and EC rejection rate were developed and observed and predicted values were compared for these terms and permeate fluxes using linear and nonlinear regressions. It was determined that osmotic pressure is a limiting condition in OMW treatment using RO membranes and that COD and EC rejection rates are useful terms to evaluate membrane performance.

The effectiveness Study of Different Membranes in Treating Industrial Wastewater

This paper focuses on the effectiveness study of different membranes in treating petroleum based wastewater. Polysulfone (PSF) and Polyether Sulfone (PES) were prepared using phase inversion method in NMP solvent. The composition of membrane was varied by manipulating the PVP additives concentration (5 wt%) in the membrane dope solution. The morphological study of prepared membranes was analysed using Field Emission Scanning Electron Microscope (FESEM) while the permeating flux and Chemical Oxygen Demand (COD) rejection rate were determined accordingly by using the refinery wastewater as the feed. The result found that the permeating flux increased as the operating pressure increased. However, for COD rejection, it was reported that only certain membrane show the best rejection. To clarify and support this finding, the membrane performance was further analyzed by determining the Total Dissolved Solid (TDS) rejection for PSF2 and PES2 membrane samples. The result showed that both membranes recorded relatively high TDS rejection which can be justified by the morphological studies of each samples. Therefore, this study proved that the membrane treatment have a high potential to treat the industrial wastewater for a larger scale.